The present invention relates to a reagent supply system for a medical analytical instrument.
Medical analytical instruments in the sense of the present invention serve to examine body fluids, especially blood. Modern instruments of this kind are largely fully automatic in operation, only the samples still having to be inserted in appropriate sample vessels and the desired analyses entered.
The invention is intended for instruments which operate with liquid reagents which are contained in reagent vessels of plastic. The instruments usually have a cooled reagent space. The reagents are transported in the instrument from the reagent vessels to the reaction vessels and there mixed with the sample, and after completion of the reaction a physically detectable change (usually a colouring) is measured as a measure of the analysis. The reagent vessels are frequently specially adapted to the reagent space of a particular instrument. By this means particularly space-saving accommodation and effective cooling of the reagents is possible. Reagent vessels and the reagent space of the instrument belonging to them, if they are functionally adapted to each other, form a system which is here called a reagent supply system.
For the transport of the reagents from the reagent vessel into the reaction vessel essentially two basically different techniques are used, namely the pipetting technique and the dispenser technique.
In the pipetting technique a pipette, usually fastened to a movable arm, dips from above through the open reagent vessel, and an appropriate amount of reagent is sucked in and transferred in the pipette (which is also known as a transfer needle) to the reaction vessel. This technique makes it possible o change the reagent vessels easily. A complicated instrument mechanism is however required. Also the transfer of reagents is relatively slow, as a result of which the throughput rate of the instrument is limited.
With the dispenser technique the reagent vessels are permanently connected individually by a line to the instrument. The connection lines are a part of a line system through which the reagents are supplied in a suitable manner (which is of no importance for the present invention) to the reaction vessels and thereby to the analysis. By this means, with relatively little mechanical complication, they are always available. This allows high analysis frequencies and thereby very rapidly operating automatic, analysers.
The dispenser technique has however considerable disadvantages with regard to handling. Usually flexible connecting tubes are introduced from above into the reagent vessels so that they end just above the vessel bottom. This is difficult and can easily lead to errors. In particular it can occur that air is sucked in if the flexible tubes do not dip deeply enough into the reagent. Also when the flexible tubes are interchanged they must each time be washed in cleaning liquid in order to prevent the transfer of reagent, especially if as is often customary--various reactions are carried out in the same channel of the instrument and accordingly different reagents are led through one flexible tube.